Engine friction model

[NaN]

I've been working on the new simulation implementation again, trying to understand a very snappy off-throttle oversteer that rwd cars exhibit.

Current vdrift implementation also has this issue, although not as pronounced due to slippy clutch(at low rpm especially). The clutch in the new implementation does lock properly and exaggerates the effect.

It seems to be caused by engine friction(braking). The torque is strong enough to kill rear wheels grip when coasting along a straight line(clutch locked, throttle off).

Thus I think the used equation/approximation might be the problem. I've been wondering if there are some "plausible" simple engine friction models to look at? Even a few numbers would help just to get an idea, fix current equation.